i was wondering if my landlord can force us to move into the apartment if it is still infested with fleasim living in an apartment building but am...

The lease you have signed will be a significant factor, as
it may contain a provision indicating responsibility for pest control. Otherwise, at
common law, a landlord typically promises his tenant the "quiet enjoyment of the
premises." If the flea infestation is so bad that you would be deprived of that private
enjoyment, then you would have a remedy at law to cancel the lease. Under any
circumstances, if you were forced to litigate this matter, it would be costly and time
consuming. Your best course of action is to ask the landlord to delay your occupancy of
the premises until such time as the exterminator's work is done. It is quite normal for
a second treatment in cases of flea infestation to kill the offspring of the fleas
earlier killed who would hatch out in the meantime. If he insists that you take
possession--or at least pay rent--then you have a difficult choice to
make.